The present invention relates to a rewinding machine for the production of rolls of web material, for example rolls of so-called tissue paper, so as to obtain small rolls of toilet paper, all-purpose drying paper and the like.
The present invention also relates to a method for the production of rolls without a central winding core.
In order to produce rolls or xe2x80x9clogsxe2x80x9d of web material, so-called rewinding machines are commonly used, in which machines a predetermined length of web material is wound onto a tubular winding core normally made of cardboard. These rolls or logs are then cut into a plurality of smaller-size rolls intended for sale. A tubular winding core section remains inside each small roll.
The winding machines of this type are divided into two categories depending on the manner in which the winding movement is provided. In a first type of rewinding machine, known as a central spindle rewinding machine, a spindle supported on support elements between a pair of side walls receives a tubular winding core on which the roll or log is formed by means of rotation of the spindle which, for this purpose, is associated with drive means. The winding movement is therefore provided centrally by the spindle.
In a second type of rewinding machine, known as a surface rewinding machine, the rotational movement of the tubular core on which the roll or log is formed is provided by peripheral members in the form of rollers or rotating cylinders and/or belts with which the roll or log is kept in contact during formation. An example of a surface rewinding machine is described in WO-A-9421545.
In both cases the end product contains a tubular core made of material different from that forming the roll.
In an attempt to obtain rolls provided with an axial hole, but without a winding core made of material different from that forming the roll, various systems have been studied. Italian Patent No. 1201390 describes a surface rewinding machine in which the cardboard tubular winding core is replaced by a recyclable winding spindle. A system for extraction of the spindle from the finished roll and for recycling said spindle towards the zone for insertion into the rewinding machine is provided downstream of the winding zone. A rewinding machine based on the same, concept is described in U.S. Pat. No. 5,421,536.
One of the difficulties of these machines and the associated winding methods relates to the first winding phase when the leading edge of the web material must be made to adhere to the spindle so as to start formation of the turns.
U.S. Pat. No. 3,869,095 describes a system in which a winding spindle receives, mounted on it, a tubular core on which a roll of wound web material is subsequently formed. The roll with its winding core is then extracted from the spindle and the tubular core remains inside the end product. In this known machine both the spindle and the tubular core are provided with holes so as to be able to suck the web material and wind it around the winding core. The spindle is kept constantly connected to suction means which follow the movement of the spindle during formation of the roll which is formed on a cradle defined by two parallel-axis rollers. Moreover, the spindle is supported by support slides which travel in lateral sliding guides and is gradually raised during winding.
EP-A-0 618 159 describes a spindle-type rewinding machine where the rolls of web material are formed around a motor-driven spindle which is subsequently extracted from the roll. During extraction, a stabilizing fluid is introduced through holes formed in the spindle so as to ensure the rigidity of the walls forming the axial hole of the roll. This publication also describes, in general terms, how the holes in the spindle may be used to suck the leading edge of web material. However, no system for applying the vacuum to the spindle is described.
Italian Patent Application No. 9652A/78, dated Dec. 1, 1978, describes a surface rewinding machine in which cardboard tubular cores which remain inside the finished roll are used for winding. A system for providing holes in the cardboard forming the tubular cores is also described. A sucking action is produced through these holes so as to cause the leading edge of the web material to adhere to the tubular core and allow winding to be started. The vacuum inside the tubular core is produced by means of one or two suction ducts which are located in a fixed position, This device, therefore, is able to function only using particularly slow winding methods in which the axis of the tubular core is not displaced or performs minimum movements until one or more winding turns have been completed. A system of blowing nozzles is also required in order to start winding of the free leading edge around the tubular core.
One object of the present invention is to provide a method and a surface winding device which allow the production of rolls or logs without a tubular core, in which the initial step for causing the free leading edge of web material to adhere to the winding spindle is efficient, fast and reliable and is suitable for high production speeds.
A further object of the present invention is to provide a method and a device of the abovementioned type, in which the step involving extraction of the spindle from the finished roll or log is easy and is not affected by the procedures used to start winding.
These and further objects and advantages, which will become clear to persons skilled in the art from a reading of the text below, are obtained by means of a surface rewinding machine of the type comprising a winding cradle for sequentially forming rolls of web material, an insertion device for inserting the winding spindles into the winding cradle and an insertion path for introducing the winding spindles into the cradle. According to the invention, a rewinding machine of this type is provided with a suction system cooperating with the spindles along at least one portion of the insertion path so as to produce a vacuum inside the spindles which have a wall which is permeable to air and typically provided with a series of holes which could also have microscopic dimensions. The suction system follows the movement of the spindles over at least part of the insertion path. This enables high production speeds to be achieved.
With this arrangement, a vacuum is produced inside each spindle during the insertion movement of the spindle into the winding cradle. During insertion, the leading edge of the web material comes into contact with the external surface of the spindle and adheres to the latter owing to the effect of the suction through the holes formed in the spindle wall. The holes may be distributed in various ways. One possibility consists in a random distribution. Alternatively, the holes may be distributed in one or more lines which extend in a helical manner along the whole spindle. Or else the holes may be distributed in annular lines arranged at suitable intervals along the axial extension. According to a further alternative, the holes are distributed along one or more aligned arrangements parallel to the spindle axis.
In a practical embodiment of the invention, the suction system may comprise a nozzle, or preferably two nozzles, one for each end of the spindle, movable along an operating path along which the nozzle or nozzles are connected pneumatically to the inside of the spindle while the latter is inserted into the winding cradle, moving along the insertion path.
The movement along the operating path and the form of the latter depend on the configuration of the rewinding machine. Generally, the present invention may be applied to any surface rewinding machine, independently of the configuration of the winding cradle. The latter may preferably consist, for example, of three winding rollers, as described in WO-A-9421545. However, the winding cradle may also be defined by different winding members, for example systems of belts, combinations of belts or rollers or the like, as known to persons skilled in the art.
Although, in principle, it is possible to use a single suction nozzle pneumatically connected to the spindle, at one end of the latter, in order to obtain a uniform vacuum and therefore a uniform suction effect along the axial extension of the spindle, it is preferable to use two nozzles, one for each end of the spindle.
When the winding cradle comprises at least one first winding roller around which the web material to be wound is fed, it is possible to envisage that the operating path of the nozzle or nozzles is substantially circular, or more precisely in the form of an arc of a circle, with the center approximately on the axis of rotation of the first winding roller. According to the preferred embodiment of the invention, it is envisaged that the first winding roller has, extending around it, a rolling surface (in a manner known per se, for example, from WO-A-9421545) which is substantially fixed with respect to the axis of rotation of the first winding roller. The operating path of the suction nozzle or nozzles extends along the channel defined between the first winding roller and the rolling surface, while the spindle rolls on the rolling surface, remaining in contact with the latter and with the surface of the first winding roller or, more precisely, with the web material conveyed around the latter.
The suction nozzle or nozzles, according to a possible embodiment of the invention, are mounted on a unit rotating about the axis of the first winding roller. It is also envisaged providing a device which controls the movement of the unit about the axis of rotation of the roller in synchronism with the movement of the insertion device which sequentially inserts the spindles along the insertion path.
Essentially, in order to avoid problems of collision of the nozzles with other machine components, the movement of the nozzle is an alternating oscillating movement instead of a continuous rotational movement. During forwards travel; the nozzles follow the movement of the spindle being inserted. Once they have completed their function, the nozzles return into the initial position with a movement in the opposite direction.
The oscillating movement of the unit supporting the nozzle or nozzles about the axis of the first winding roller may be obtained, for example, by means of a system comprising a motor and a pinion and crown-wheel transmission system. However, according to a particularly advantageous embodiment of the invention, the rotating unit may support a small shaft which has an axis perpendicular to the axis of rotation of the first winding roller and on which a wheel is mounted in an idle manner. Said wheel is made to roll over a surface not rotating with respect to the axis of rotation of the first winding roller and over an annular surface of the first winding roller, perpendicular to its axis. In this way, as will be clarified more fully below, the unit supporting the nozzle or nozzles moves at a speed equal to the speed of movement of the individual spindles along the insertion path. This solution is particularly advantageous because it is mechanically simple and can be easily synchronized with the spindle movement, without the need for special measures.
Essentially, suction may be maintained until winding of the first turn of web material onto the spindle has been completed.
Further advantageous features of the rewinding machine according to the invention are indicated in the accompanying dependent claims.
The winding method according to the invention envisages using suction holes on the spindle and causing a leading portion of the web material to adhere to said spindle by means of suction through said holes obtained by producing a vacuum inside the spindle. Essentially, winding is of the surface type and the suction is maintained inside the spindle along a section of the insertion path which it follows within the winding means.
In one mode of implementation of the method according to the invention, the winding spindle is introduced into a winding cradle along an insertion path. A vacuum is temporarily produced along this path, inside the winding spindle. The spindle may perform a rolling movement along the insertion path. The vacuum inside the spindle may be obtained by arranging next to one end thereof (or preferably both ends) a suction nozzle which follows the movement of the spindle over at least a portion of the insertion path.
Further advantageous features and modes of implementation of the method according to the invention are described in the accompanying claims.